àn​hào

password

暗号 (暗號) àn​hào
password noun
a pre-arranged secret word, phrase, or countersign used to identify oneself or gain access

The soldier shouted in the dark, 'Halt! Give the password!'

signal noun
a secret signal, sign, or gesture used for identification or communication

They agreed to use the flowerpot on the windowsill as a signal.

Frequency

Movie subtitles
5.54 per million appears in 2% of films
Written text
1.84 per million

Sources

Definitions
CC-CEDICT